With the rising cost of conventional fuels, such as coal, oil and natural gas, along with diminishing domestic reserves of each, attention has been directed to developing alternative energy sources. Among the most convenient energy sources readily available is the thermal radiation of the sun. Although this source of energy is readily adaptable for heating purposes, it has been relatively difficult and expensive to convert into usable mechanical work. As such, the vast potential of solar energy has yet to be fully realized.
Some of the applications to which solar generated mechanical energy is suitable can be found in the need to power pumps and machinery in remote regions where conventional energy sources are not available. These applications include the need of power for irrigation pumps in remote areas of underdeveloped countries or other areas where it is either impossible or impractical to supply a conventional energy source, such as electricity. Also, the need of employing solar mechanical energy is finding application in the space exploration program, as artificial satellites and manned space craft remain in orbit for extended periods of time without access to any energy sources other than the sun. Furthermore, in solar heat exchangers of the circulating-water type, it is desirable to eliminate the need for electric pumps to circulate the water, and replace them with solar powered pumps thereby further reducing the reliance on conventional energy sources.
Various efforts have been made to harness the energy of the sun and convert it into useful mechanical work. Among these efforts is the process of using photovoltaic cells to generate electrical current which is then used to power electric motors which, in turn, drive pumps or other machinery. Such systems have found little practical application because of the exorbitant cost of the equipment needed for such systems, and also because of the poor system efficiency resulting from the conversions of solar energy first to electrical energy and then to mechanical energy. As such, these systems have been little more than experimental apparatus in test laboratories or space satellites.
Systems have been developed to convert solar energy directly into mechanical energy, as shown in the disclosure of U.S. Pat. No. 4,227,866. These systems necessitate very large, and very expensive, solar collectors to generate the required work pressure. As such, these ungainly devices require a substantial amount of ground space to support them and thus are limited in application, generally to rural underdeveloped areas where ground space is not of any major concern. These devices are not suitable for installation in space satellites, of on the roof top of a building, or any other location where space is at a premium.
Despite the extensive efforts to harness the energy of the sun, no practical embodiment has yet been developed to convert solar energy into usable mechanical energy efficiently and economically, or to do so in an embodiment readily adaptable for incorporation in a system where a large amount of space is not available.